I mean, I'm not sure I'd call any build 'elite' when its description involves "Your mates will have to carry you levels 1-3, at level 4 you'll be pretty sweet, then at level 5-7 you'll be about as comparable as any other purely directed caster doing similar things, while at level 8 and beyond you'll be utterly gimped and crutched compared to your companions who, by that point, have 18 or above in their core stat, while you have to keep a particular helmet welded to your head for all time, in order to be just slightly *worse* than them."
I mean imagine twinning a Scorching Ray with Hex applied to target for 18D6 damage!
You can't. That's not how Twin Spell works.
They just have to carry you until Blighted Village, which yes will likely be level 3, which is 900 experience. Its about 15% into EA.
I can only account for Levels 1-4 as that is all we have. Once we have full levels and multiclass this build goes out the window.
I assume you referring to the fact that twin spell requires you to choose a second target - which wouldn't have Hex. Fair point.
I myself am critical of this build because I think its a lot of work for a minor payoff, but sort of a funny synergy. In real 5e with all classes and multi available it would make way more sense to multiclass.
I would also grab the Sword of Justice and throw Tyr's Protection on you for 19 AC - free of charge. Then swap it with the any other weapon.
Feel free to corect me ...
But doesnt them both (Tyr's Protection and Hex) require concentration, and therefore excluding each other? O_o
And if not ... remember to do this trick before combat, since equiping weapon costs action now.

Yes, you would of course do it before combat and then unequip it. And also you would have to choose to use Hex and drop your Tyr's protection or not. This would be a situational decision depending on the targets in the environment. A high target environment it would make sense to keep the Protection up and focus on shatter, thunderwave, magic missile. A single high health target I would go with the Hex to up the damage on scorching ray.